1. Field of the Invention
The invention relates to a method for forming a fuel igniting glow plug, and more specifically toward a method for forming a layered heating element therefor.
2. Related Art
Glow plugs can be utilized in any application where a source of intense heat is required for combustion. As such, glow plugs are used as direct combustion initiators in space heaters and industrial furnaces and also as an aid in the initiation of combustion when diesel engines must be started cold. Glow plugs are also used as heaters to initiate reactions in fuel cells and to remove combustible components from exhaust systems.
With regard to the example of diesel engine applications, during starting and particularly in cold weather conditions, fuel droplets are not atomized as finely as they would be at normal running speeds, and much of the heat generated by the combustion process is lost to the cold combustion chamber walls. Consequently, some form of additional heat is necessary to aid the initiation of combustion. A glow plug, located in either the intake manifold or in the combustion chamber, is a popular method to provide added heat energy during cold start conditions.
The maximum temperature reached by the glow plug heating element is dependent on the voltage applied and the resistance properties of the components used. This is usually in the range of 1,000-1,300° C. Materials used in the construction of a glow plug are chosen to withstand the heat, to resist chemical attacks from the products of combustion and to endure the high levels of vibration and thermal cycling produced during the combustion process.
To improve performance, durability and efficiency, new materials are constantly being sought for application within glow plug assemblies. For example, specialty metals and ceramic materials have been introduced into glow plug applications. While providing many benefits, these exotic materials can be difficult to manufacture in high production settings. Sometimes, they are not entirely compatible with other materials, resulting in delamination and other problems. Another common problem with specialty materials manifests as tolerance variations when formed in layers resulting from cumbersome and inefficient manufacturing techniques.
Accordingly, there is a need for improved methods for forming glow plugs, and in particular the heating element portion of a glow plug using specialty materials which results in a precision formed, durable monolithic structure.